FRIDAY, May 29, 2015 (HealthDay News) -- A new drug appears to harness a person's immune system to fight the most common form of lung cancer, according to new clinical trial findings.

The drug, nivolumab, reduced patients' risk of death from non-small cell lung cancer by 27 percent compared with patients who received docetaxel, a commonly used chemotherapy medication, researchers said.

The study results are scheduled for presentation Saturday at the annual meeting of the American Society of Clinical Oncology, in Chicago.

Nivolumab -- marketed as Opdivo -- primarily helps patients whose tumor cells carry a trait that allows their cancer to avoid detection by the immune system. As a result, overall median survival was 12.2 months in the nivolumab group compared to 9.4 months in the docetaxel group, the researchers reported.

Also, only one in 10 patients experienced serious side effects with nivolumab, compared to more than half of patients taking docetaxel, said lead study author Dr. Luis Paz-Ares, a professor of medicine at Hospital Universitario 12 de Octubre in Madrid, Spain.

The study was funded, in part, by the drug's maker, Bristol-Myers Squibb.

"While nivolumab appears to be more potent against this most common lung cancer, it is important to note that it is also far easier on patients compared to the standard second-line treatment, docetaxel," Paz-Ares said.

Dr. Nagashree Seetharamu, a medical oncologist with North Shore-LIJ Cancer Institute in Lake Success, N.Y., called the findings "exciting."

"Immunotherapy is going to take treatment of cancer to a whole new level, and in lung cancer, it's going to be paradigm-changing," he said.

Lung cancer is the most common cancer worldwide, and the leading cause of cancer deaths in the United States, according to the study authors.

Non-small cell lung cancer, the most common form, accounts for 85 percent of all lung cancers. More than two-thirds of those are non-squamous cell cancers.

Nivolumab is in a class of drugs called immune checkpoint inhibitors, which essentially prod the immune system to attack and destroy cancer cells, said Dr. Gregory Masters, a lung cancer specialist at the Helen F. Graham Cancer Center in Newark, Del.

"These drugs I suspect are here to stay," he said. "They're a big part of the future of treating cancer."

Nivolumab targets a protein called the programmed death-1 (PD-1) receptor. This protein normally prevents the immune system from attacking healthy cells, Masters said.

Some lung tumor cells can take advantage of PD-1's normal function to evade immune detection. They carry a molecule called PD-L1 that masks their abnormal nature, Masters said. These molecules make cancer cells look like healthy cells, as far as the PD-1 protein is concerned.

Nivolumab essentially removes PD-1 from the equation, Masters said. By turning off this mechanism, "you release the immune system to do its work," he explained.

This clinical trial focused on using nivolumab to combat non-squamous, non-small cell lung cancer, with 582 patients randomly assigned to receive either nivolumab or docetaxel. All had advanced lung cancer that had grown worse even after receiving powerful chemotherapy.

Docetaxel works by interfering with the division of cancer cells.

With nivolumab, "we are not actually targeting the tumor cells," Paz-Ares said. "We are mainly targeting the immune system of the host, and forcing a response against the tumor. It's a totally new concept."

Not only did the nivolumab-treated patients live about three months longer on average, they also had a 19.2 percent response rate compared with 12.4 percent for docetaxel, the researchers said. Further, the response lasted significantly longer -- about 17.1 months on average for nivolumab versus 5.6 months for docetaxel.

The drug only appears to help people with the PD-L1 trait, however, Paz-Ares said. About 55 percent of patients had a high enough PD-L1 level to make the drug an effective treatment.

PD-L1 is detected through biopsy of lung tumor cells. "It's not really a standard test you can just order," Masters said. "The companies that are developing these drugs have the ability to test for this. I suspect in the near future that will be something we can order from a standard lab."

The new drug is very expensive, Masters said, but may prove itself cost-effective.

"If a person can be treated for a few months and then remain off treatment for a year, that may be a more cost-effective method of treatment than standard chemotherapy," he said.

Data and conclusions presented at meetings are usually considered preliminary until published in a peer-reviewed medical journal.